Moissanite

The mineral moissanite was discovered by Henri Moissan while examining rock samples from what is now called Meteor Crater located near Canyon Diablo, Arizona, US in 1893. At first, he mistakenly identified the crystals as diamonds, but in 1904 he identified the crystals as silicon carbide. Artificial silicon carbide had been synthesized in the lab by Edward G. Acheson in 1891, just two years before Moissan's discovery. The mineral form of silicon carbide was named in honor of Moissan later on in his life. == Geological occurrence ==

In its natural form, moissanite remains very rare. Until the 1950s, no source for moissanite other than as presolar grains in carbonaceous chondrite meteorites had been encountered. Then, in 1958, moissanite was found in the Green River Formation in Wyoming, US and, the following year, as inclusions in the ultramafic rock kimberlite from a diamond mine in Yakutia in the Russian Far East. Yet the existence of moissanite in nature was questioned as late as 1986 by the American geologist Charles Milton. Discoveries show that it occurs naturally as inclusions in diamonds, xenoliths, and such other ultramafic rock such as lamproite. ==Meteorites==

Analysis of silicon carbide grains found in the Murchison meteorite has revealed anomalous isotopic ratios of carbon and silicon, indicating an extraterrestrial origin from outside the Solar System. 99% of these silicon carbide grains originate around carbon-rich asymptotic giant branch stars. Silicon carbide is commonly found around these stars, as deduced from their infrared spectra. The discovery of silicon carbide in the Canyon Diablo meteorite and other places was delayed for a long time as carborundum (SiC) contamination had occurred from man-made abrasive tools. == Physical properties ==

The crystalline structure is held together with strong covalent bonding similar to those in diamonds, Colors vary widely and are graded from D to K range on the diamond color grading scale. == Sources ==

Moissanite was introduced to the jewelry market as a diamond alternative in 1998 after Charles & Colvard (formerly known as C3 Inc.) received patents to create and market lab-grown silicon carbide gemstones, becoming the first firm to do so. By 2018 all patents on the original process world-wide had expired. As of 1998, Charles & Colvard makes and distributes moissanite jewelry and loose gems under the trademarks Forever One, Forever Brilliant, and Forever Classic. Other manufacturers market silicon carbide gemstones under trademarked names such as Amora. On the Mohs scale of mineral hardness (with diamond as the upper extreme, 10) moissanite is rated as 9.5. Because of its hardness, it can be used in high-pressure experiments, as a replacement for diamond (see Diamond anvil cell). Silicon carbide is a mainstream semiconductor for high-power and high-temperature electronics. Commercial SiC power devices first entered mass production in the early 2000s with SiC Schottky barrier diodes, followed by SiC MOSFETs in the 2010s. Relative to silicon devices, SiC offers a wider bandgap, higher critical electric field, and superior thermal conductivity, enabling lower switching and conduction losses, higher operating temperatures, and operation at higher voltages and frequencies. making it useful in radiation dosimetry. ==See also==